command 0.0.8

A lightweight framework for designing interactive CLI applications

To use this package, run the following command in your project's root directory:

Manual usage
Put the following dependency into your project's dependences section:

This package provides sub packages which can be used individually:

command:lib - A lightweight framework for designing interactive CLI applications

command:grammar - Generator for the command grammar

command:varstore - A minimal D application.

command:greeter - A minimal D application.

command:typed - A minimal D application.


This is a simple command-line framework that I devised while writing a "very secret" project for an internship.


This library is still in-dev.

PLEASE NOTE: By default, the library will *NOT* spawn a new thread and read from stdin. This functionality is *opt-in*, and you MUST compile the library with the `cli` version for this. This is done via:

// dub.sdl
subConfiguration "command" "cli"
// dub.json
"subConfigurations": {
    "command": "cli"

ADDITIONAL NOTE: Compiling the library with the `cli` will bring in `linenoise` as a dependency.

Design Goals:

  • Lightweight
    • Minimal dependencies (only 2, but 1 is optional)
  • Portable
  • Easy to use


Untyped example:

class TestExample {
    // name, description, min args, max args
    @Command("hello", "Hello, World!", 0, 0)
    string hello(string[] args) {
        return "Hello, World!";

    @Command("user", "Say hello to someone!", 1, 1)
    string hello_user(string[] args) {
        return "Hello, " ~ args[0] ~ "!";

mixin RegisterModule!TestExample;

Typed example:

class TestExample {
    // example with no parameters
    @TypedCommand("hello", "Hello, World!", 0, 0)
    string hello() {
        return "Hello, World!";

    // any POD parameter is allowed here (float, string, double, integer, etc)
    // as well, the return type may be any POD
    @TypedCommand("user", "Say hello to someone!", 1, 1)
    string hello_user(string user) {
        return "Hello, " ~ user ~ "!";

    @TypedCommand("meaning_of_life", "What is the meaning of life?", 0, 0)
    int meaningOfLife() {
        return 42;

then, in the CLI:

> test.hello()
Hello, World!
> test.user("Foo")
Hello, Foo!
> test.user(test.hello())
Hello, Hello, World!!

(also found in command:greeter)


  • Proper return types
    • Avoid using strings as a type everywhere
  • Small standard library for ease of use
    • No user-defined functions however
      • By design, we're not trying to be a scripting engine
  • Well-defined instantiation order
    • In the end, this won't matter (since you can't call until the engine has been fully initialized), but might be worth investigating
  • Harrison Ford
Sub packages:
command:lib, command:grammar, command:varstore, command:greeter, command:typed
0.0.8 2020-Nov-23
0.0.7 2020-Nov-07
0.0.6 2020-Nov-07
0.0.5 2020-Nov-07
0.0.4 2020-Nov-07
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